Increasingly more vehicles of the recent generation are being equipped with charging devices. In order to achieve the target demands and the legal requirements, it is imperative to promote development in the complete drive train and also to optimize the individual components as well as the system as a whole with respect to their reliability and efficiency.
Known examples include, for example, exhaust gas turbochargers, in which a turbine wheel is driven by the exhaust gas flow of the internal combustion engine. A compressor wheel, which is arranged with the turbine wheel on the common shaft, compresses the fresh intake air for the engine. By this means, the amount of air or oxygen, which is available to the engine for combustion, is increased, which in turn leads to an increased performance of the internal combustion engine. The disadvantage in exhaust gas turbocharges is that their rotation rate or performance is dependent on the exhaust gas flow, thus on the engine load. At low engine speeds, in particular, this may negatively affect the effectiveness and efficiency of exhaust gas turbochargers.
An alternative to exhaust gas turbochargers is presented by electric turbochargers, also called eBoosters. In these turbochargers, the shaft, on which the compressor wheel is arranged, is not driven by the exhaust gas flow from the engine or via a turbine wheel, but instead by an electric motor driving the shaft. For this purpose, a rotor is arranged on the shaft with a stator around the rotor. Shaft, rotor, and stator are surrounded by a stator housing. At high load and during performance peaks, these components heat up strongly. To prevent temperatures in the turbocharger that are too high, it is known to provide cooling ducts, through which a coolant is supplied, for cooling the stator in the stator housing. However, in these turbochargers, very high temperatures still arise in the area of the not-cooled rotor. This limits the performance during demand peaks. The same applies for electric or electrically supported charging devices, like hybrid versions made from an exhaust gas turbocharger and an electric turbocharger, in which the drive of the compressor wheel is possible both by the exhaust gas flow via a turbine wheel and also via an electric motor arranged on the shaft, most often between the turbine wheel and the compressor wheel.
The object of the present invention is accordingly to provide a charging device for an internal combustion engine which enables cooling of the rotor.